fix: free strings after being read to prevent potential memory leaks

impls/monero.ts/checksum.ts

@@ -19,7 +19,7 @@ export class ChecksumError extends Error {
  * @returns {ChecksumError} which contains information about why checksum failed
  */
 export async function validateChecksum(): Promise<ChecksumError | null> {
-  const cppHeaderHash = readCString(await dylib.symbols.MONERO_checksum_wallet2_api_c_h());
+  const cppHeaderHash = await readCString(await dylib.symbols.MONERO_checksum_wallet2_api_c_h());
   const tsHeaderHash = moneroChecksum.wallet2_api_c_h_sha256;
 
   const errors: string[] = [];
@@ -30,14 +30,14 @@ export async function validateChecksum(): Promise<ChecksumError | null> {
     errorCode++;
   }
 
-  const cppSourceHash = readCString(await dylib.symbols.MONERO_checksum_wallet2_api_c_cpp());
+  const cppSourceHash = await readCString(await dylib.symbols.MONERO_checksum_wallet2_api_c_cpp());
   const tsSourceHash = moneroChecksum.wallet2_api_c_cpp_sha256;
   if (cppSourceHash !== tsSourceHash) {
     errors.push(`ERR: CPP source file check mismatch ${cppSourceHash} == ${tsSourceHash}`);
     errorCode++;
   }
 
-  const cppExportHash = readCString(await dylib.symbols.MONERO_checksum_wallet2_api_c_exp());
+  const cppExportHash = await readCString(await dylib.symbols.MONERO_checksum_wallet2_api_c_exp());
   const tsExportHash = moneroChecksum.wallet2_api_c_exp_sha256;
   if (cppExportHash !== tsExportHash) {
     if (Deno.build.os !== "darwin") {

impls/monero.ts/src/bindings.ts

@@ -523,6 +523,14 @@ export const symbols = {
     result: "pointer",
   },
   //#endregion
+
+  "MONERO_free": {
+    nonblocking: true,
+    // void* ptr
+    parameters: ["pointer"],
+    // void
+    result: "void",
+  },
 } as const;
 
 type MoneroTsDylib = Deno.DynamicLibrary<typeof symbols>;

impls/monero.ts/src/pending_transaction.ts

@@ -22,7 +22,7 @@ export class PendingTransaction {
     const error = await dylib.symbols.MONERO_PendingTransaction_errorString(this.#pendingTxPtr);
     if (!error) return null;
 
-    return readCString(error) || null;
+    return await readCString(error) || null;
   }
 
   async throwIfError(sanitize = true): Promise<void> {
@@ -50,7 +50,7 @@ export class PendingTransaction {
     );
     if (!result) return null;
     await this.throwIfError();
-    return readCString(result) || null;
+    return await readCString(result) || null;
   }
 
   async amount(): Promise<bigint> {
@@ -72,7 +72,7 @@ export class PendingTransaction {
     );
     if (!result) return null;
     await this.throwIfError(sanitize);
-    return readCString(result) || null;
+    return await readCString(result) || null;
   }
 
   async txCount(): Promise<bigint> {

impls/monero.ts/src/transaction_info.ts

@@ -50,12 +50,12 @@ export class TransactionInfo {
 
   async description(): Promise<string> {
     const description = await dylib.symbols.MONERO_TransactionInfo_description(this.#txInfoPtr);
-    return readCString(description) || "";
+    return await readCString(description) || "";
   }
 
   async subaddrIndex(): Promise<string> {
     const subaddrIndex = await dylib.symbols.MONERO_TransactionInfo_subaddrIndex(this.#txInfoPtr);
-    return readCString(subaddrIndex) || "";
+    return await readCString(subaddrIndex) || "";
   }
 
   async subaddrAccount(): Promise<number> {
@@ -64,7 +64,7 @@ export class TransactionInfo {
 
   async label(): Promise<string> {
     const label = await dylib.symbols.MONERO_TransactionInfo_label(this.#txInfoPtr);
-    return readCString(label) || "";
+    return await readCString(label) || "";
   }
 
   async confirmations(): Promise<bigint> {
@@ -77,7 +77,7 @@ export class TransactionInfo {
 
   async hash(): Promise<string> {
     const hash = await dylib.symbols.MONERO_TransactionInfo_hash(this.#txInfoPtr);
-    return readCString(hash) || "";
+    return await readCString(hash) || "";
   }
 
   async timestamp(): Promise<bigint> {
@@ -86,7 +86,7 @@ export class TransactionInfo {
 
   async paymentId(): Promise<string> {
     const paymentId = await dylib.symbols.MONERO_TransactionInfo_paymentId(this.#txInfoPtr);
-    return readCString(paymentId) || "";
+    return await readCString(paymentId) || "";
   }
 
   async transfersCount(): Promise<number> {
@@ -99,6 +99,6 @@ export class TransactionInfo {
 
   async transfersAddress(index: number): Promise<string> {
     const transfersAddress = await dylib.symbols.MONERO_TransactionInfo_transfers_address(this.#txInfoPtr, index);
-    return readCString(transfersAddress) || "";
+    return await readCString(transfersAddress) || "";
   }
 }

impls/monero.ts/src/utils.ts

@@ -1,13 +1,20 @@
+import { dylib } from "../mod.ts";
+
 export type Sanitizer = () => void | PromiseLike<void>;
 
 const textEncoder = new TextEncoder();
 export function CString(string: string): Deno.PointerValue<string> {
   return Deno.UnsafePointer.of(textEncoder.encode(`${string}\x00`));
 }
 
-export function readCString(pointer: Deno.PointerObject): string;
-export function readCString(pointer: Deno.PointerValue): string | null;
-export function readCString(pointer: Deno.PointerValue): string | null {
+// This method reads string from the given pointer and frees the string
+// SAFETY: Do not use readCString twice on the same pointer as it will cause double free
+//         In that case just use `Deno.UnsafePointerView(ptr).getCString()` directly
+export async function readCString(pointer: Deno.PointerObject): Promise<string>;
+export async function readCString(pointer: Deno.PointerValue): Promise<string | null>;
+export async function readCString(pointer: Deno.PointerValue): Promise<string | null> {
   if (!pointer) return null;
-  return new Deno.UnsafePointerView(pointer).getCString();
+  const string = new Deno.UnsafePointerView(pointer).getCString();
+  await dylib.symbols.MONERO_free(pointer);
+  return string;
 }

impls/monero.ts/src/wallet.ts

@@ -153,7 +153,7 @@ export class Wallet {
       const error = await this.errorString();
       throw new Error(`Failed getting address from a wallet: ${error ?? "<Error unknown>"}`);
     }
-    return readCString(address);
+    return await readCString(address);
   }
 
   async balance(accountIndex = 0): Promise<bigint> {
@@ -174,7 +174,7 @@ export class Wallet {
     const error = await dylib.symbols.MONERO_Wallet_errorString(this.#walletPtr);
     if (!error) return null;
 
-    return readCString(error) || null;
+    return await readCString(error) || null;
   }
 
   async throwIfError(sanitize = true): Promise<void> {
@@ -253,7 +253,7 @@ export class Wallet {
       const error = await this.errorString();
       throw new Error(`Failed getting subaddress label from a wallet: ${error ?? "<Error unknown>"}`);
     }
-    return readCString(label);
+    return await readCString(label);
   }
 
   async setSubaddressLabel(accountIndex: number, addressIndex: number, label: string): Promise<void> {